The University of Colorado Anschutz Medical Campus, in partnership with a tribal Early Head Start and behavioral health program, is implementing a study to assess the relationship between major environmental stressors and hair cortisol for American Indian children and their caregivers, as well as the role of parent-child relationships in buffering children from the effects of these stressors on development. The aims of the project are to: (1) examine the nature, extent and developmental course of environmental stressors among American Indian children between the ages of 10 and 36 months; (2) assess hair cortisol as a marker of toxic stress; and (3) adapt two promising interventions for strengthening the parent-child relationship for mobile (e.g. text messaging, social media) delivery and piloting. The study has been approved by the tribal Institutional Review Board; it also employs a Community Advisory Board consisting of Early Head Start parents, teachers, and staff, as well as representatives from other tribal community programs serving young children and families. The study will yield information about stress and its effects among American Indian children and their caregivers, establish a mobile (mHealth) parenting intervention that increases the reach of critical parenting interventions within this tribal context, and inform efforts for serving broader populations of tribal children and families.